When a percussive tool such as a hammer is moved to strike a surface of an object, part of the kinetic energy developed is utilized in doing the desired work on the object, part is dissipated as heat, and part is converted into potential energy in the form of distortion in the striking surface of the hammer. Hammer recoil has been encountered with hammer configurations including either exposed striking heads or a skeletal hammer design wherein the hammer heads are wholly received in an encasing to prevent sparking or the like during hammer use. The distortion of the striking surface of the hammer has potential energy much the same way as a compressed spring. It is this potential energy that causes the hammer to recoil or bounce back from the surface of the object being struck.
If a force is applied to the tool or hammer at the same time that the recoil would normally take place, and which force is equal and opposite to the potential energy, the two forces cancel each other and the energy is converted to heat. The cancellation of the two forces provides the hammer with an advantageous "dead-blow" characteristic.
Various attempts have been made to apply a force sufficient to prevent recoil in hammers and other striking articles. One attempt involves placing a slidable slug behind the striking head on the hammer. Alternatively, some hammers are designed with a powdered shot filled cavity in a head portion of the hammer. Such attempts have not, however, been completely successful in preventing recoil of the hammer from the surface of the object being struck.
Those hammers having slidable slugs arranged behind the striking head have not been very successful. During use of such hammers or tools, the slugs themselves develop potential energy when the hammer impacts against a surface of an object being struck and tend to recoil thus causing undesirable vibration or oscillation in the hammer.
The concept of using powdered shot material in a chamber defined in the head area of the hammer likewise has problems associated therewith. The required size of the chamber for holding a sufficient amount of powdered shot material and, thus, the size of the hammer is often out of proportion for a particular weight of the hammer. Moreover, unless a specific mixture of powdered shot material is utilized, the powdered material is often not very helpful in reducing the rebound of the hammer from that surface being struck.
It has been a prevalent practice in the trade to construct hammers with wooden handles. Recently, however, hammers having an internal metal skeleton surrounded by a molded cosmetic plastic body have become increasingly popular. The internal metal skeleton provides the hammer with stiffness and strength while the surrounding plastic body provides the desired aesthetic features for the hammer. A severe drawback with this design, however, is that the impact at the striking moment is transmitted through the metal handle core to the users hand, thus increasing efforts and labor of the user and thereby reducing the operating efficiency of the hammer.
While using a hammer, it is not unusual to miss the object to be struck with the head of the tool. Accordingly, impact forces are directed against the handle portion of the tool. The aesthetic plastic body surrounding the internal metal skeleton is not commonly designed for such impacts and is often damaged from such "overstrikes" of the hammer. Although damage to the handle portion of the tool from any single overstrike of the hammer may be slight, an accumulation of overstrikes directed against the plastic handle portion of the tool can result in significant damages to the hammer.
Thus there is both a need and a desire for a percussive tool which provides a so called "dead-blow" characteristic by preventing rebounding of the striking head on the hammer and which reduces the impact transmitted through the tool to the user thereof. A need and a desire furthermore exists for a composite hammer design including a plastic body but which has increased overstrike strength in the handle portion of the tool.